It's serious, it's just not widespread since the majority of players are level 30. Instead of streamlining the system, Riot ignored it which is why so many people are getting away with selling level 30 accounts. Levels 1-29 should revolve around learning the actual game, but instead you don't get access to runes (finally fixing it), masteries (season 6 made it worse), and summoner spells. Why should someone go through 7 levels to reach level 8 and finally unlock the most popular summoner spell
? There isn't really a reason and I can't imagine they sell THAT many xp boosts for the money to warrant their notorious leveling system. You don't get to actually play League of Legends as it is until level 30. It's like, oh you want to play our "free" game? Put a month of time into a game sort of like it and then you can start from scratch on the real game.